Gene Therapy: Virus Restores Sight

Photo: Gene Therapy

In the new therapy, viruses able to penetrate the many cell layers of the retina are used to shuttle a corrective gene into cells with a defective gene; © UC Berkeley/David Schaffer Lab

Researchers at the University of California, Berkeley, have developed a new method to insert genes into eye cells that could greatly expand gene therapy to help restore sight to patients with blinding diseases.

These can range from inherited defects like retinitis pigmentosa to degenerative illnesses of old age, such as macular degeneration. Unlike current treatments, the new procedure – which takes a little as 15-minutes – is surgically non-invasive, and it delivers normal genes to difficult-to-reach cells throughout the entire retina.

Over the last six years, several groups have successfully treated people with a rare inherited eye disease by injecting a virus with a normal gene directly into the retina of an eye with a defective gene. Despite the invasive process, the virus with the normal gene was not capable of reaching all the retinal cells that need fixing. "Sticking a needle through the retina and injecting the engineered virus behind the retina is a risky surgical procedure," said David Schaffer, professor of chemical and biomolecular engineering and director of the Berkeley Stem Cell Center at the University of California, Berkeley. "But doctors have no choice because none of the gene delivery viruses can travel all the way through the back of the eye to reach the photoreceptors – the light sensitive cells that need the therapeutic gene."

"Building upon 14 years of research, we have now created a virus that you just inject into the liquid vitreous humor inside the eye and it delivers genes to a very difficult-to-reach population of delicate cells in a way that is surgically non-invasive and safe. It is a 15-minute procedure, and you can likely go home that day." The engineered virus works far better than current therapies in rodent models of two human degenerative eye diseases, and can penetrate photoreceptor cells in the eyes of monkeys, which are like those of humans.

Schaffer and his team are now collaborating with physicians to identify the patients most likely to benefit from this gene-delivery technique and, after some preclinical development, hope soon to head into clinical trials, he said.; Source: University of California – Berkeley